Summary: Automated Control for Elastic Storage
Harold C. Lim Shivnath Babu Jeffrey S. Chase
Duke University
Durham, NC, USA
{harold, shivnath, chase}@cs.duke.edu
ABSTRACT
Elasticity--where systems acquire and release resources in response
to dynamic workloads, while paying only for what they need--is
a driving property of cloud computing. At the core of any elas-
tic system is an automated controller. This paper addresses elastic
control for multi-tier application services that allocate and release
resources in discrete units, such as virtual server instances of pre-
determined sizes. It focuses on elastic control of the storage tier, in
which adding or removing a storage node or "brick" requires rebal-
ancing stored data across the nodes. The storage tier presents new
challenges for elastic control: actuator delays (lag) due to rebalanc-
ing, interference with applications and sensor measurements, and
the need to synchronize the multiple control elements, including
rebalancing.
We have designed and implemented a new controller for elas-